Coaxial connectors utilizing an insulating medium sometimes experience slippage or movement of the insulating medium with respect to the inner and outer conductors. This is a fairly common experience with commercially available coaxial cable assemblies such as SMA and SSMA. This slippage or in some instances separation of the insulation from and within the connector is also common under extreme ranges of temperature particularly in the range from -55.degree. C. to 125.degree. C.
Cable connector manufacturers have devised different techniques to correct the insulation slippage problem. One correction technique, known as epoxy cross pinning involves drilling a hole transversely through the outer conductor towards and through the insulation layer. Epoxy is then injected into this region to the inner conductor thus trapping the insulation and inner conductor. The inner conductor has a smaller diameter (undercut) in this region to hold the inner conductor in place. Often rather than having this undercut, the inner conductor is provided with grooves and knurls to prevent slippage of the center conductor.
The epoxy cross-pinning technique has several disadvantages. Since the epoxy used in the hole is not an adhesive but is instead a bulk material, a weak arrangement in the connector results. Further, the drilling of holes in the connector is expensive requiring a second operation or a special machine. There is also a tendency for the RF energy to leak out through the holes since the epoxy acts as a signal path. The drilling and injection of epoxy is time consuming and requires a curing process. The presence of epoxy having a dielectric constant appreciably higher than that of the insulation such as PTFE causes disturbances to the radio frequency energy and results in undesirable reflections which requires compensation to minimize these reflections.
Another technique to capture insulation in a coaxial cable is known as upsetting. In this method, several holes are drilled transversely substantially but not entirely through the outer conductor. After the insulation has been installed between the outer conductor and center conductor, a tool is used to punch through the holes drilled causing a burr to embed into the insulating material. Epoxy is then applied to "cover up" the openings. Disadvantages similar to those associated with epoxy cross-pinning also apply to this technique.
A third technique known as fish hook or barbs may also be used. In this application, the insulation is pressed into barbed regions created on the inner surface of the outer conductor. The insulation is prevented from slipping in one direction, however there remains easy movement in the opposite direction. The barbed technique also does not work well with insulating materials such as polytetrafluoroethylene because of its crushable properties and slick bearing surface. Further, this barbed region is difficult to manufacture.
Other techniques also exist but are less common.
There is a need for a coaxial connector assembly for capturing the insulation and center conductor of a coaxial cable connector to prevent movement of the components which does not create objectionable disturbances to the signal and maintains a high degree of shielding effectiveness with the coaxial cable.